1. Field of the Invention
The present invention relates to a focal plane shutter for a camera.
2. Description of the Related Art
Recently, two types of focal plane shutters for cameras have been known: shutters including two shutter blade groups, which are called a front blade (group) and a rear blade (group), and shutters including a single shutter blade group. The former shutters are used in both digital cameras and silver-salt film cameras, while the latter shutters are used only in digital cameras. In either one of the two types of shutters, each shutter blade group includes a plurality of arms, each of which is attached to a shutter base plate in a pivotable manner at one end thereof, and a plurality of blades which are successively arranged on the arms toward free ends of the arms and supported by the arms in a pivotable manner. One or two blade chambers are formed between the shutter base plate and an auxiliary base plate (also referred to as a cover plate), and each shutter blade group is disposed in the corresponding blade chamber. Each shutter blade group performs an opening-closing operation in response to a rotation of a driving member.
An opening for an imaging optical path is formed in the shutter base plate at a central section thereof. A support plate is disposed at a side of the opening such that a plate surface of the support plate is parallel to the shutter base plate, and is attached to the shutter base plate with a predetermined space provided between the support plate and the shutter base plate. The above-described driving member is disposed in the space. In general, an electromagnet is also disposed in the space. The electromagnet is attached to the support plate and starts the rotation of the driving member in a certain direction at a predetermined time in a shooting operation.
A printed wiring board is stacked on the support plate, and a switch operated by the rotation of the driving member is attached to the printed wiring board. Japanese Unexamined Patent Application Publication No. 8-201877 (hereinafter referred to as Patent Document 1) discloses a structure in which the switch is used as a flash synchronization switch. Japanese Unexamined Patent Application Publication No. 2002-55377 (hereinafter referred to as Patent Document 2) proposes that the switch can also be used as a switch for detecting a malfunction of the driving member or the shutter blade group.
The printed wiring board is commonly manufactured using a glass epoxy copper clad laminate (also called a glass epoxy substrate), which is rigid. In addition, as described in Patent Document 1, the switch includes two flexible contact members, which are bonded to the printed wiring board at first ends thereof and are provided with contact portions at second ends thereof. In a normal state, portions near the second ends are brought into contact with different end surfaces of the printed wiring board by elasticity of the contact members, so that the contact portions are in a non-contact state. When the driving member is rotated in a certain direction and is caused to push one of the contact members, the pushed contact member moves away from the end surface of the printed wiring board. Then, the contact portion of the pushed contact member comes into contact with the contact portion of the other contact member and pushes the other contact member away from the end surface of the printed wiring board. Then, when the driving member is rotated in the opposite direction, the contact members are caused to return to the positions in the normal state by the elasticity thereof.
Accordingly, the two contact members repeatedly come into contact with and move away from the end surfaces of the printed wiring board each time the shooting operation is performed. However, in the case where the printed wiring board is rigid, since the glass epoxy copper clad laminate is used, there is a risk that small dust will be generated from the end surfaces of the printed wiring board when the contact members repeatedly come into contact with and move away from the end surfaces. In addition, there is also a risk that the surface state of the end surfaces will be changed, which leads to a contact failure of the switch or a shift in the contact time. Therefore, in order to solve such a problem, Japanese Unexamined Patent Application Publication No. 2004-212877 (hereinafter referred to as Patent Document 3) discloses a structure in which a switch attachment plate made of a synthetic resin and a flexible printed wiring board are stacked on a support plate. Two contact members are bonded to the flexible printed wiring board at first ends thereof, and portions of the contact members near second ends thereof are brought into contact with and moved away from end surfaces of the switch attachment plate.
In order for the above-described switch to reliably operate, it is, of course, necessary to reliably bring the contact portions of the two contact members into contact with each other precisely at a predetermined time. In the structure described in Patent Document 3, the two contact members are brought into contact with and moved away from the end surfaces of the switch attachment plate made of synthetic resin each time the shooting operation is performed. Therefore, unlike the case in which the glass epoxy copper clad laminate is used, the problem that the small dust will be generated from the end surfaces when the contact members repeatedly come into contact with and move away from the end surfaces and the problem that the surface state of the end surfaces will be changed do not occur. Therefore, the switch can be reliably operated.
However, as is well known, this type of products have individual differences after assembly, owing to processing tolerance and assembly tolerance of components. Therefore, even when no problems are expected after the products are installed in cameras and sold as in the structure of Patent Document 3, it is necessary to perform inspection after the assembly and make an adjustment if necessary since individual differences are caused in the manufacturing process, as is well known. In such a case, a worker slightly changes the shapes of the contact members so that a predetermined function can be obtained. However, since it is necessary to perform such an adjustment in the assembly phase and not before the installation of the product, the adjustment is difficult and it takes a long time even for a skilled worker to make the adjustment.